In a known engine, a bypass channel of a turbocharger is provided with a valve for adjusting the air volume. Patent Literatures 1 and 2 (PTLs 1 and 2) disclose engines of this type.
The engine of PTL 1 includes an intake manifold, an exhaust manifold, a main fuel injection valve that injects liquid fuel to the cylinder for combustion, a gas injector that mixes gaseous fuel with air supplied from the intake manifold, a turbocharger that compresses air, and an intercooler that cools the compressed air compressed in the turbocharger and supplies the cooled compressed air to the intake manifold. The engine of PTL 1 is configured such that a main throttle valve is provided at the connection between a turbocharger outlet and an intercooler inlet, and an exhaust bypass vale is disposed in an exhaust bypass channel connecting an exhaust manifold outlet and a turbocharger outlet to each other. This configuration of PTL 1 is intended to control the air volume responsively with respect to a load variation when the engine is operated in a gas mode.
The engine of PTL 2 includes a main turbocharger, a subturbocharger, an intake switching valve that opens and closes an intake passage disposed downstream of a compressor of the subturbocharger, and an exhaust switching valve that opens and closes an exhaust passage disposed downstream or upstream of a turbine of the subturbocharger. This engine includes a control device. The control device is configured as follows. The control device actuates only the main turbocharger by closing both the intake switching valve and the exhaust switching valve in a low-speed range, and actuates both the main turbocharger and the subturbocharger by opening both the intake switching valve and the exhaust switching valve in a high-speed range. When the low-speed range shifts to the high-speed range, the control device controls an exhaust bypass valve disposed downstream or upstream of the subturbocharger such that the exhaust bypass valve is open to a small degree and controls an intake bypass valve disposed in an intake bypass passage bypassing a compressor of the subturbocharger such that the intake bypass valve is closed before opening of the exhaust switching valve to thereby increase a run-up revolution speed of the subturbocharger. The engine of PTL 2 includes a first intake temperature sensor disposed at a compressor inlet of the subturbocharger and a second intake temperature sensor disposed at a compressor outlet of the subturbocharger and the intake switching valve. The engine includes a failure determination means for causing a display means to display that a failure of the intake bypass valve occurs at the closed valve side if the intake temperature value from the first intake temperature sensor is a predetermined first set value or more while the exhaust bypass valve is controlled to open to a small degree or if the intake temperature value from the second intake temperature sensor is a predetermined second set value or more while the exhaust bypass valve is controlled to open to a small degree. When a failure of the intake bypass valve occurs at the closed side, this configuration of PTL 2 enables early detection of this failure and issues an alarm of this failure to a driver of the vehicle.